Movable storage systems have gained widespread popularity as a means for maximizing the storage capacity of a confined space. These devices typically consist of a plurality of storage units which can be moved independently along a pair of guide rails mounted on the floor to create an access aisle between any two adjacent storage units.
Safety considerations make it desirable that the storage units not be moveable when a person is present in the access aisle. For that reason, much effort has gone into developing various types of mechanisms which enable the storage units to be selectively locked in place so that the access aisle is not closed unintentionally. Many of the locking and unlocking mechanisms available heretofore require manual actuation by a user. Not surprisingly, users often forget to actuate these mechanisms before entering the access aisle, thereby creating a potential for injury.
In view of the foregoing, attempts have been made to provide passive locking and unlocking systems which automatically lock the storage units from moving toward one another once an access aisle between the storage units has been created. One such system is disclosed in U.S. Pat. No. 5,160,189. This patent describes a storage unit having an internal toothed locking wheel operatively connected to the wheels of the storage unit, a pair of actuating members connected by pawls to the locking wheel, and a scissors mechanism connected between adjacent storage units. As the storage units are moved away from one another to create an access aisle therebetween, the scissors mechanism actuates the actuating members to move the pawls into engagement with the locking wheel in such a way that the locking wheel and thus the storage units can continue moving in the same direction, but so that the locking wheel and thus the storage units are prevented from moving in a reverse direction. A major disadvantage of this system is that, once the pawls have engaged the locking wheel, continued movement of the storage units away from one another in order to enlarge the access aisle causes the pawls to ratchet over the locking wheel so that an annoying clicking sound is produced. This sound is particularly disturbing in the office environments in which these movable storage systems are frequently situated.
There therefore exists a need for improvements in the locking systems used to maintain an open aisle between the adjacent storage units of a movable storage system, and more particularly in those locking systems which are actuated passively without the need for a deliberate action on the part of the user. Preferably, such locking systems will have a simple construction requiring little or no maintenance and will operate silently so as to not create a distraction in the work environment.